The present invention relates generally to a hydropneumatic damping device. The hydropneumatic damping device comprises an inner cylinder having an axis and two ends, namely a first end and a second end. A central cavity is defined within the inner cylinder between said two ends. An outer container surrounds the inner cylinder. The outer container has first and second ends adjacent the first and second ends of the inner cylinder, respectively. An annular cavity is defined between the inner cylinder and the outer container. First and second closure means are provided for closing the first and second ends of the cylinder and the container, respectively. Piston rod passage means extend through the first ones of the closure means. Fluid passage means are provided between the central cavity and the annular cavity adjacent the second closure means. First fluid throttling means are associated to the fluid passage means. A piston rod axially extends through the piston rod passage means and into the central cavity. A piston unit is mounted on the piston rod within the central cavity and defines two working chambers within the central cavity. A first working chamber is defined adjacent the first closure means and a second working chamber is provided adjacent the second closure means. Fluid connecting means are provided for connecting the two working chambers across the piston unit. Second fluid throttling means are associated to said fluid connecting means. A body of liquid is provided at least within the central one of the cavities. A body of gas is provided within the annular cavity.
The first closure means comprise a cavity-closing unit surrounding the piston rod and having an axially inner end adjacent the first working chamber and an axially outer end. Securing means are provided on the container adjacent the first end thereof for axially securing said cavity-closing unit with respect to the first end of the cylinder. A sealing unit engages the piston rod and has an outer side exposed to atmosphere and an inner side adjacent the cavities and axially outward of the axially inner end of the cavity-closing unit. Venting passage means are provided between the first working chamber and the annular cavity. These venting passage means extend across the cavity-closing unit on the inner side of the sealing unit. Check valve means are associated to the venting passage means permitting gas residues to flow from the first working chamber towards the annular cavity and preventing reverse flow. These check valve means comprise an annular check valve member in frictional sliding engagement with the piston rod for axial movement with the piston rod towards a sealing position during inward movement of the piston rod and towards an opening position during outward movement of the piston rod. First and second abutment means are provided for defining said sealing position and said opening position of the annular check valve member, respectively.
Such a hydropneumatic damping device is known from U.S. Pat. No. 4,287,970. In this patent the second abutment means are defined by an annular abutment disc which is fixed with respect to the cavity-closing unit by deformation of the material of the cavity-closing unit. The assembling of the cavity-closing unit and the annular abutment disc is rather difficult and expensive. Moreover, there is as risk that the cavity-closing unit is damaged during the deformation step. Moreover, it is to be observed that considerable axial forces act upon the annular abutment disc in operation such that a highly reliable fixation of the annular abutment disc is necessary with respect to the cavity-closing unit. Therefore, the assembling of the cavity-closing unit and the abutment disc is still more difficult.
It is a primary object of this invention to avoid the above-mentioned difficulties of the known type of hydropneumatic damping device. More particularly, it is an object of the invention to provide a hydropneumatic damping device in which at least the second abutment means are fixed to the closing unit such as to reliably withstand the axial forces ocurring in operation.